1. Field of the Invention
This invention relates to Michael adducts of (substituted) cyclopentadiene and aliphatic or inertly-substituted aliphatic esters of .alpha.,.beta.-ethylenically unsaturated carboxylic acids. In one aspect, this invention relates to a process for preparing these adducts. In other aspects, this invention relates to Diels-Alder adducts of these Michael adducts and to polyester compositions comprising the Diels-Alder adducts.
2. Description of the Prior Art
Taylor et al., "The Michael Condensation. VII. Activation of the Methylene Group by Carbon-Carbon Unsaturation", J. Org. Chem., 6, 696 (1941) teach the Michael condensation of cyclopentadiene with both benzalacetophenone and benzal-p-bromoacetophenone. These condensations are conducted at elevated pressure and over extended reaction times and produce oxime derivatives of the desired Michael adducts in low yields. The adducts themselves were not isolated.
H. A. Bruson, "The Chemistry of Acrylonitrile. I. Cyanoethylation of Active Methylene Groups", J. Am. Chem. Soc., 64, 2457 (1942) and U.S. Pat. No. 2,280,058, teaches the addition of acrylonitrile to compounds having the grouping C.dbd.C--CH--C.dbd.C in a carbocycle in the presence of benzyltrimethylammonium hydroxide. These condensations are by way of Michael addition and yield poly-cyanoethylation products. Bruson reports that attempts to replace acrylonitrile with acrylic esters were unsuccessful.
U.S. Pat. No. 3,409,659 by R. L. Pruett and S. Raines teaches a modification of Bruson's addition of acrylonitrile to cyclopentadiene. By using a 4-6 molar excess of cyclopentadiene, maintaining the temperature of the reaction mass at between -5.degree. and 0.degree. C., and extending the addition and post-addition reaction periods, Pruett and Raines were able to obtain low yields (from 11 percent to a maximum of 30 percent) of mono-(.beta.-cyanoethyl)cyclopentadiene.
U.S. Pat. No. 3,524,890 by E. F. Cox teaches a base-catalyzed addition of cyclopentadiene and a vicinal epoxide to produce hydroxy-containing substituted cyclopentadienes. Cox does not teach said addition with any other electrophile.
The above teachings of Taylor et al., Bruson, Pruett and Raines, and Cox are the extent of the known, based-catalyzed additions of cyclopentadiene.
The known process for preparing the Michael adducts of (substituted) cyclopentadiene and esters, e.g., functional cyclopentadiene derivatives such as methyl cyclopentadiene propionate, is illustrated by the teaching of R. L. Schaaf and C. T. Lenk. "Ferrocenes. VII. Ferrocenes from Monofunctional Cyclopentadienes", J. Org. Chem., 29, 3430 (1964). Therein, an equimolar amount of sodium cyclopentadienide in tetrahydrofuran is reacted with methyl 3-bromopropionate at -70.degree. C. to yield 45 percent of said product. This process also yields a mole of sodium bromide for each mole of alkyl halide consumed. T. Kunitomo, S. Tanimoto and R. Oda, "Synthesis of Condensation Polymers from Cyclopentadienyl-Alkane Carboxylic Esters", Kogyo Kagaku Zasshi, 68, 1973-6 (1965), teach a similar alkylation followed by a Diels-Alder addition of the resulting functional diene with methyl acrylate. The resulting bicyclic diester monomers were independently condensed with ethylene glycol and hexamethylenediamine to yield the respective polyester and polyamide.